Some minor cleanups to df.c. Also, with Erik's blessing, changed name of
'format' function to 'make_human_readable_str'.
diff --git a/utility.c b/utility.c
index 0ace3eb..7c7af15 100644
--- a/utility.c
+++ b/utility.c
@@ -1798,7 +1798,7 @@
 #endif
 
 #ifdef BB_FEATURE_HUMAN_READABLE
-const char *format(unsigned long val, unsigned long hr)
+const char *make_human_readable_str(unsigned long val, unsigned long hr)
 {
 	int i=0;
 	static char str[10] = "\0";